SpendGuard

A 2-line wrapper around your OpenAI or Anthropic client that blocks an over-budget API call before it happens — no surprises at the end of the month.

from spendguard import SpendGuard

guard = SpendGuard(workspace="my-app", ceiling_usd=20.0)
client = guard.wrap_openai(OpenAI())          # or wrap_anthropic(Anthropic())

# Call the client exactly as normal — SpendGuard intercepts transparently.
# If the estimated cost would push cumulative spend past 25% of the $20 ceiling,
# it raises BudgetExceededError before the API call is made.
response = client.chat.completions.create(model="gpt-4o", messages=[...])

Install

pip install spendguard

For more accurate pre-call token counting on OpenAI models:

pip install spendguard[tiktoken]

How it works

SpendGuard wraps your existing client object. Every call goes through two steps:

1. Pre-call estimate — approximates the input token count and adds the max output tokens × the model's per-token rate. If cumulative_spend + estimate > ceiling × threshold_pct, it raises BudgetExceededError before the network call.
2. Post-call commit — reads the provider's actual usage numbers from the response and records the real cost.

The default threshold is 25% of the ceiling (threshold_pct=0.25). This means a single call can consume at most 25% of your monthly budget — it is a guardrail against a single runaway call, not a hard cap at 100%.

Supported providers and models

Usage

Basic setup

from openai import OpenAI
from spendguard import SpendGuard

guard = SpendGuard(workspace="my-product", ceiling_usd=20.0)
client = guard.wrap_openai(OpenAI())

try:
    response = client.chat.completions.create(
        model="gpt-4o",
        messages=[{"role": "user", "content": "Hello"}],
        max_tokens=512,
    )
except BudgetExceededError as e:
    print(f"Blocked: {e}")

Anthropic

from anthropic import Anthropic
from spendguard import SpendGuard

guard = SpendGuard(workspace="my-product", ceiling_usd=20.0)
client = guard.wrap_anthropic(Anthropic())

response = client.messages.create(
    model="claude-sonnet-4-6",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello"}],
)

Overriding a block on purpose

When you explicitly want to allow a call that would be blocked (e.g., a one-time large batch job), use track() with override=True:

with guard.track(override=True):
    response = client.chat.completions.create(...)   # never blocked

The override only applies inside the with block and does not persist.

Inspecting current spend

summary = guard.get_summary()
# {"ceiling_usd": 20.0, "spent_usd": 1.23, "reserved_usd": 0.0, "threshold_pct": 0.25}

Workspace isolation

Each SpendGuard instance is scoped to a workspace string. When you run multiple products or feature flags, give each its own workspace so their budgets are tracked independently.

Out of scope for v0.1

• Streaming calls (stream=True) — explicitly rejected with a clear error.
• Embeddings, images, audio, and other non-chat/messages endpoints.
• Persistent spend across process restarts (resets on SpendGuard() construction).

Persistence and streaming support are planned for v1.0.

Feedback

Found a bug or have a feature request? Open an issue — all feedback welcome.

License

MIT